US5495529A - Digital sound level control apparatus - Google Patents

Digital sound level control apparatus Download PDF

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Publication number
US5495529A
US5495529A US08/161,928 US16192893A US5495529A US 5495529 A US5495529 A US 5495529A US 16192893 A US16192893 A US 16192893A US 5495529 A US5495529 A US 5495529A
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Prior art keywords
signal
digital
pcm
circuit
telephone
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US08/161,928
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English (en)
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Toshio Honda
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NEC Corp
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NEC Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/002—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G7/00—Volume compression or expansion in amplifiers
    • H03G7/007—Volume compression or expansion in amplifiers of digital or coded signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/002—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems
    • H04M9/008—Multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/40—Applications of speech amplifiers

Definitions

  • This invention relates to the main unit of a key telephone system including a segment coder for companding (compressing and decompressing) a digital audio signal, and more particularly to a sound level control apparatus for use with an apparatus of the type described above.
  • FIG. 1 shows a conventional monitor circuit of a digital audio apparatus.
  • a digital sound level control apparatus of the type mentioned above includes, as disclosed in Japanese Patent Application No. 72457/1986, entitled “Monitor Circuit” shown in FIG. 1, a circuit for adjusting the sound level output by sending a code signal to monitor body section 52 from sound level adjusting switch 54 and multiplying the PCM audio signal of the output of monitor signal extraction circuit 58 by the code signal to define the monitor sound level through sound level conversion memory 57, digital audio convertor 56 and analog amplifier 55.
  • the conventional digital sound level control apparatus includes a ROM in which a predetermined conversion table is stored. Accordingly, the conventional digital sound level control apparatus is disadvantageous in that much labor and time are required to write the conversion table into the ROM upon assembly of a digital key telephone system and in that, once the ROM is incorporated into a telephone apparatus, the sound level cannot be varied flexibly in conformity with the circuit with which the telephone apparatus actually is used.
  • the present invention provides a digital sound level control apparatus which eliminates setting of a contrast table between sound levels and conversion codes into a ROM.
  • a first digital sound level control apparatus for a main unit of a digital key telephone system, the main unit including a circuit control section per telephone circuit, a PCM conversion section having a segment coder for compressing with the ⁇ -Law PCM characteristic per telephone circuit, a main control section for designating pad multipliers which defines an attenuation value corresponding to the employed telephone circuit, a digital sound level control apparatus per telephone circuit and digital time switch means for switching speech paths, the digital sound level control apparatus comprising:
  • a second digital sound level control apparatus for the main unit of the digital key telephone system, the main unit including a circuit control section per telephone circuit, a PCM conversion section having a segment coder for compressing with the ⁇ -Law PCM characteristic per telephone circuit, a main control section for designating pad multipliers which defines an attenuation value corresponding to the employed telephone circuit, a digital sound level control apparatus per telephone circuit and digital time switch means for switching speech paths, the digital sound level control apparatus comprising:
  • first discrimination means for discriminating a segment region of a ⁇ -Law PCM conversion characteristic polygonal line from a segment region signal of a PCM input data signal which is outputted from the PCM conversion section, the PCM input data including a polarity signal, a segment region signal and a step signal;
  • first calculation means for calculating a first level signal which is a data value before compression using the output signal of the first segment region discrimination means and the step signal of the PCM input data signal;
  • multiplication means for multiplying a pad multiplier by the first level signal to output a second level signal
  • second segment region discrimination means for discriminating its segment region by comparing the second level signal with the coding threshold values of segment regions based on the segment compression and decompression characteristic
  • second calculation means for calculating its step signal based on the second level signal, the coding threshold signal and the intrinsic variation amount per step of the segment region;
  • register means for forming a ⁇ -Law PCM digital signal combining the original polarity signal, the calculated segment region signal and the calculated step signal.
  • the first level signal of the digital sound level control apparatus described above may be a value obtained by adding the value which is obtained by multiplying the intrinsic variation amount per step of its segment region by the step signal to the basic normalization level signal of said segment region, or a value obtained by adding the value which is obtained by multiplying the intrinsic variation amount per step of its segment region by the step signal to the coding threshold value of said segment region.
  • FIG. 1 is a block diagram of a monitor circuit of an example of a conventional digital sound level control apparatus
  • FIG. 2 is a block diagram of an embodiment of the main unit of a key telephone system.
  • FIG. 3 is a block diagram of pad conversion section 13 shown in FIG. 2.
  • the main unit of key telephone system 1 comprises circuit control section 11, PCM conversion section 12, main control section 15, pad conversion section 13 and time divisional switch 14.
  • the present invention is incorporated in pad conversion section 13 and main control section 15.
  • Circuit control section 11 serves as an interface to telephone circuit 2 and reports to main control section 15 the classification of telephone circuits employed for incoming telephone calls.
  • PCM conversion section 12 converts an incoming analog data signal into a ⁇ -Law PCM digital signal.
  • Pad conversion section 13 outputs data signal D O which is modified from PCM input data signal D I from PCM conversion section 12 to digital data having a controlled sound level by decompressing, multiplying by pad multiplier P d sent from main control section 15 and compressing to ⁇ -Law PCM digital data.
  • Main control section 15 outputs multiplier P d signal to pad conversion section 13 corresponding to the employed incoming telephone circuit by discriminating by notification from circuit control section 11.
  • Time division switch 14 switches telephone calls by switching the connection of the PCM highway.
  • PCM input data signal D I is an 8-bit signal wherein the MSB of the eighth bit serves as polarity signal P, the three bits of the seventh to fifth bits serve as a segment region (described as region signal A hereafter) which identifies a segment, and the remaining four bits of the fourth to first bits serve as step signal bits S representative of a position in a segment.
  • Region signal A includes intrinsic variation signal A 1 representative of the variation amount per step of the level value in the segment region before compression, basic normalization level signal A 2 (4,191 in region 8; 2,079 in region 7; 1,023 in region 6 and the like) representative of a reference point for each segment region before compression, and coding threshold value A 3 (4,063 in region 8; 2,015 in region 7; 991 in region 6 and the like) representative of the start point of each region before compression.
  • Pad conversion section 13 converts compressed PCM input data into data of the level before compression with reference to the basic normalization level signal before compression, multiplies the data of the converted or decompressed level by a pad multiplier to convert the data into a predetermined sound volume, compresses the volume signal again, and outputs the thus-compressed volume signal to the time division switch.
  • Pad conversion section 13 includes register 31 for temporarily storing input data signal Di, another register 32 for temporarily storing a pad multiplier signal, region discrimination circuit 33 for discriminating region signal A in PCM input data signal D I and dividing region signal A into intrinsic variation signal A 1 , normalization reference level signal A 2 and coding threshold value A 3 , multiplication circuit 34 for multiplying step signal S in PCM input data D I by intrinsic variation amount signal A 1 , addition circuit 35 for adding basic normalization level signal A 2 to the output signal of multiplication circuit 34 to output input level signal L I , another multiplication circuit 36 for multiplying input level signal L I by pad multiplier signal P d to output output level signal L O , comparison region discrimination circuit 37 for comparing output level signal L O and coding threshold value A 3 to determine to which region output level signal L O corresponds, and outputting region signal A' based on the determination, subtraction circuit 38 for subtracting coding threshold value A 3 of the region from output level signal L O , division circuit 39 for dividing the output of subtraction circuit 38 by intrinsic variation signal A
  • Analog audio data received from telephone circuit 2 are inputted by way of circuit control section 11 and converted into a PCM signal by PCM conversion section 12.
  • circuit control section 11 determines whether the received call is originated from an extension line or another subscriber line and notifies the result of the determination to main control section 15.
  • PCM input data signal D I as audio data coded by PCM coding by PCM conversion section 12 is outputted to pad conversion section 13.
  • pad multiplication value signal P d representative of an attenuation amount is instructed from main control section 15 to pad conversion section 13, and PCM output data signal D O for which the sound volume difference has been adjusted is outputted to time division switch section 14 in which a PCM highway is exchangeably connected.
  • the sound level difference among calls from extension lines and other subscriber lines can be eliminated, by the way that multipliers to designate attenuation amounts are set and stored in main control section 15 in such a manner that the attenuation amount is 0 dB for a call received from outside line 2 but is 6 dB for a call received from an extension line.
  • PCM input data signal D I from PCM conversion section 12 is inputted to 8-bit register 31 while pad multipier value signal P d for determination of the attenuation amount from main control section 15 is inputted to 4-bit register 32.
  • Region discrimination circuit 33 discriminates a region from region signal A in PCM input data signal D I inputted to register 31 and outputs basic normalization level signal A 2 intrinsic to the region, intrinsic variation amount signal A 1 intrinsic to the region determined from region signal A, and coding threshold value A 3 .
  • Multiplication circuit 34 multiplies intrinsic variation value signal A 1 by step signal (bits 4 to 1) S of PCM input signal D I , and the result of the addition of the result of the multiplication to basic normalization signal A 2 by addition circuit 35 is outputted as input level signal L I . Meanwhile, polarity signal (bit 8) P of PCM input data signal D I is not inputted to region discrimination circuit 33 but is outputted as is as a polarity signal of PCM output data signal D O .
  • the pad multiplication value signal instructed from main control section 15 is inputted to and then outputted from register 32.
  • Multiplication circuit 36 multiplies input level signal L I outputted from addition circuit 35 by pad multiplication value signal P d outputted from register 32 and outputs the result of the multiplication as output level L O .
  • Segment region comparison discrimination circuit 37 which compares coding threshold value A 3 determined from region signal A by region discrimination circuit 33 and output level signal L O outputted from multiplication circuit 36, determines the region to 10 which output level signal L O corresponds, and outputs corresponding region signal (bits 7 to 5) A'.
  • step signal (bits 4 to 1) S' the result of subtraction of coding threshold value A 3 from output level signal L O by subtraction circuit 38 is divided by intrinsic variation signal A 1 determined from region signal A' by division circuit 39, and the result of the division is outputted as step signal (bits 4 to 1) S'.
  • PCM output data signal D O after conversion into a pad value instructed by main control section 15 from polarity signal (bit 8) P, region signal (bits 7 to 5) A' and step signal (bits 4 to 1) S' is stored once into and then outputted from register 40.
  • main control section 15 outputs pad multiplication value P d to pad conversion section 13 in accordance with the type of circuit. Where the number of types of circuits involved is great, it may be possible to provide means for setting correspondence tables so that the corresponding pad multiplier may be outputted for each of the types of circuits.
  • input level L I is obtained by the addition of the product between intrinsic variation signal A 1 and step signal S to the normalization reference level signal, it may be obtained otherwise by the addition of the product between intrinsic variation A 1 and step number S to coding threshold value A 3 .
  • a region signal and a step signal corresponding to a circuit from which a call is received are outputted from the digital sound level control apparatus of the present invention by calculating the region signal, and the step signal there is an advantage in that the reception sound level can be held substantially constant irrespective of from which telephone circuit a call is received.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Sub-Exchange Stations And Push- Button Telephones (AREA)
  • Interface Circuits In Exchanges (AREA)
US08/161,928 1992-11-26 1993-11-24 Digital sound level control apparatus Expired - Fee Related US5495529A (en)

Applications Claiming Priority (2)

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JP31703092 1992-11-26
JP4-317030 1992-11-26

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US5495529A true US5495529A (en) 1996-02-27

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US (1) US5495529A (de)
EP (1) EP0599653B1 (de)
CA (1) CA2110031C (de)
DE (1) DE69326670T2 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5715309A (en) * 1995-03-03 1998-02-03 Advanced Micro Devices, Inc. Conversion of compressed speech codes between attenuated and unattenuated formats
KR100520161B1 (ko) * 1998-12-30 2005-11-24 삼성전자주식회사 국설교환기와isdn키폰시스템과의코딩변환회로
WO2010093917A2 (en) * 2009-02-13 2010-08-19 University Of Florida Research Digital sound leveling device and method to reduce the risk of noise induced hearing loss

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3688097A (en) * 1970-05-20 1972-08-29 Bell Telephone Labor Inc Digital attenuator for non-linear pulse code modulation signals
US3752970A (en) * 1971-12-22 1973-08-14 Bell Telephone Labor Inc Digital attenuator
GB2215944A (en) * 1987-12-28 1989-09-27 Iwatsu Electric Co Ltd Key telephone system
US5070524A (en) * 1989-10-30 1991-12-03 Kabushiki Kaisha Toshiba Telephone system
US5224159A (en) * 1991-01-24 1993-06-29 Kabushiki Kaisha Toshiba Key telephone system provided with telephone sets connectable to add-on modules
US5259001A (en) * 1991-12-17 1993-11-02 Motorola, Inc. ADPCM decoder with an integral digital receive gain and method therefor
US5287106A (en) * 1987-05-07 1994-02-15 Sgs-Thomson Microelectronics Spa Circuit for PCM conversion of an analog signal, with improvement in gain-tracking
US5301205A (en) * 1992-01-29 1994-04-05 Sony Corporation Apparatus and method for data compression using signal-weighted quantizing bit allocation

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3688097A (en) * 1970-05-20 1972-08-29 Bell Telephone Labor Inc Digital attenuator for non-linear pulse code modulation signals
US3752970A (en) * 1971-12-22 1973-08-14 Bell Telephone Labor Inc Digital attenuator
US5287106A (en) * 1987-05-07 1994-02-15 Sgs-Thomson Microelectronics Spa Circuit for PCM conversion of an analog signal, with improvement in gain-tracking
GB2215944A (en) * 1987-12-28 1989-09-27 Iwatsu Electric Co Ltd Key telephone system
US5070524A (en) * 1989-10-30 1991-12-03 Kabushiki Kaisha Toshiba Telephone system
US5224159A (en) * 1991-01-24 1993-06-29 Kabushiki Kaisha Toshiba Key telephone system provided with telephone sets connectable to add-on modules
US5259001A (en) * 1991-12-17 1993-11-02 Motorola, Inc. ADPCM decoder with an integral digital receive gain and method therefor
US5301205A (en) * 1992-01-29 1994-04-05 Sony Corporation Apparatus and method for data compression using signal-weighted quantizing bit allocation

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5715309A (en) * 1995-03-03 1998-02-03 Advanced Micro Devices, Inc. Conversion of compressed speech codes between attenuated and unattenuated formats
KR100520161B1 (ko) * 1998-12-30 2005-11-24 삼성전자주식회사 국설교환기와isdn키폰시스템과의코딩변환회로
WO2010093917A2 (en) * 2009-02-13 2010-08-19 University Of Florida Research Digital sound leveling device and method to reduce the risk of noise induced hearing loss
WO2010093917A3 (en) * 2009-02-13 2011-01-20 University Of Florida Research Digital sound leveling device and method to reduce the risk of noise induced hearing loss
US8804975B2 (en) 2009-02-13 2014-08-12 University Of Florida Research Foundation, Incorporated Digital sound leveling device and method to reduce the risk of noise induced hearing loss

Also Published As

Publication number Publication date
EP0599653B1 (de) 1999-10-06
DE69326670T2 (de) 2000-02-10
EP0599653A3 (de) 1994-12-07
DE69326670D1 (de) 1999-11-11
EP0599653A2 (de) 1994-06-01
CA2110031C (en) 1997-04-08
CA2110031A1 (en) 1994-05-27

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